CYP24A1 and chronic obstructive pulmonary disease: Both 1,25(OH)2D and TX527 upregulated CYP24A1 (p < 0.05) (Figure 6c,d) and cathelicidin mRNA expression (p < 0.05) (Figure 6e,f) in PBEC from both unused donor lungs and COPD explant lungs.